When one say's NHibernate is missing VS integration, I don't think it's the GUI Modeler that they are missing. It's the fact that they can't point at a database and hit "GO"...I think model first is important, but not everyone works that way.

Low friction prototypes are often the start to more complex finished products. We don't need complexity in prototypes; we tailor our finished works to our problem domain - this is where we tweak the API (away from the GUI) to fit the specific requirements of our problem. The ability to quickly create prototypes from the IDE is incredibly important. Without IDE integration, creating these prototypes is difficult...friction.

The thing that a MS solution offers is IDE integration, which you do not find in the NHibernate suite. If I could go to the NHForge.com site and download a VS plug-in, point at a db, and then start playing...I would be much more inclined to use NHIbernate in a project.